Accelerator for the vulcanization of rubber



Patented May 30, 1933 UNITED STATES PATENT OFFICE,

ADRIEN CAMERON, OF MONTREAL, QUEBEC, CANADA, ASSIGNOR, BY MESNE ASSIGN-IMENTS, TO THE EOESSLERE: HASSLACHER CHEMICAL COMPANY, A CORPORATION OFDELAWARE ACCELERATOR non. THE vnncnnrznrron or RUBBER l v No Drawing.Original application filed January 20, 1928, Serial No. 82,612, BatentNo. 1,796,240 dated March 10, 1931, and in Germany January 19, 1927.Divided and. this application filed March 28, 1928.

Serial N0. 265,523. 7

The object of this invention is to provide a substance for aiding thevulcanization of rubber which will be cheap while at the same timepowerful, rapid, non-poisonous, hard but of low softening and meltingpoint and of a brittle nature so as to allow of easy pulverizationanddistribution in a rubber mix. A further object is to provide in thissame substance a material which will retard the aging of the finishedrubber. This application is a division of my copending appli cation S.N. 82,612 issued March 10, 1931, as U. S. Patent No. 1,796,240.

My invention comprises an improved'prodnot formed by the condensation ofacetaldehyde with aniline in the presence of an acidic catalyst andincludes a process of treating rubber, balata, gutta percha, or similarmaterial with this improved acetaldehyde aniline condensation productand vulcanizing. My invention also includes the product of the process.This application concerns a species of material which is claimed broadlyin an application S. N. 82,618 filed by me of even date herewith. andissued as U. S. Patent 1,754,010 on April 8, 1930.

The condensation products of acetaldehyde and aniline have been used invarious forms for some time as accelerators in the art of vulcanizingrubber. These substances vary greatly in nature and activity due to thevarying methods of formation and to the many different ratios suggestedand employed between the acetaldehyde and aniline. Most of thesesubstances however are of an undesirable soft pitchy nature beingneither hard materials nor free flowing liquids, because of this softand sticky nature the material is extremely difficult to handle. Some ofthe so-called hard products are unsuitable in many cases since theground particles agglomerate on standing. A recently suggest ed processis a secondary treatment of these soft materials with a further aldehydeaddition after a primary condensation has been effected. I have foundthat such further aldehyde additions are unnecessary and a waste. In myU. S. Patent 1,562,146 of Nov. 17, 1925 I have disclosed and claimed onemethod of preparing improved condensation products of aldehydesandamines'and one application of this process is the formation 'of animproved acetaldehyde-aniline condensation product. 7 v I have nowdiscovered a new process of preparing a hard acetaldehyde-anilinecondensation product. I have found that it is possible to obtain a hardproduct suitable for use as an accelerator of vulcanization of rubber bycondensing the aniline and acetaldehyde in the presence of acidcatalystsl This new roduct can be round to a fine a I powder and 111 notagglomerate after grinding; it has excellent accelerating properties andgreatly extends the life of the rubber article in which itis used. Ithas been proposed to prepare various rubber compound ing materials suchas age resistors, accelerators and conditioners from aldehydes andamines in aqueous acid solutions. In these, however, large amounts ofacid are present and this not only alters the course of the reaction andproduces a different type' of product, but also serves with the water todissolve out certain constituents of the mix. The product of this typeof high acid reaction requires neutralization with alkalies and othertreatment such as washing with water to render it suitable for use inrubber. My condensation product is prepared with acid catalysts in thesubstantial absence of water and has no definite melting point. I havefound that high acid concentrations during the preparation of thecondensate has unfavorable efi ects on the accelerating properties ofthe product. Furthermore the water removes constituents which arevaluable in acceleratlng vulcanization. r

One preferred method of practicing my effects of the hydrochloric acidwhen it is I added.

' and 50 lbs. acetaldehyde'(1.3 pounds excess The total amount of acidiccatalyst used is less than of the weight of the acetaldehyde and anilineso that neutralization of the acid with alkalies is unnecessary.Furthermore the reaction is carried out with essentially dryacetaldehyde and'aniline; thus the only water present is that due to Ithe condensation reaction and that incidentally added, with thecatalyst. These points are given to clearly distinguish this processfrom those processes where substantial amounts of water are used as thereaction medium and considerable amounts of acid used to dissolve outcertain constituents in the reaction product.

I preferably first prepare a catalyst consisting of an addition productof zinc chloride and aniline by mixing these in reacting proportions, e.g. 2 moles of aniline to one mole of zinc chloride. 0.22 lb. of thiszinc chloride-aniline product is then'added to 51.5 pounds of aniline ina jacketed kettle with thorough stirring to prevent the zincchloride-aniline from settling out. Cooling water is now circulated inthe kettle jacket chloric acid solution is now added in a period of 1015 minutes, with stirring continued as before. Cooling water is stillbeing circulated. Due to the catalytic effect upon adding the acid, thekettle temperature rises sharply, reaching about 8085 C. As soon as thistemperature begins to fall showing a completion of the major part of thereaction, the cooling water is shut-off and the water jacket emptied.Thus the heat of the reaction is utilized as fully as possible andserves to carry the reaction to completion. The charge is stirred forabout 30 minutes longer and then blown out into pans to cool. Theproduct is then ground and dried. The softening point is about 80 C.when tested as described below. The material thus prepared has achocolate brown color when in the form of lumps which on grinding formsa reddish brown powder.

In measuring the hardness of this material 'I find that a good index isthe softening point and flowing point. A suitable method for these,determinations is described in Allens Commercial Organic Analysis,

I Fourth Edition, Volume III, pages 7 677 for the softening and flowingpoint of asphalts. Briefly, this consists in spreading some of theground material on a thin microscope slide placed on a mercury bathheated by a small flame. IThe temperaturev rise is adjusted to about 23C. per minute. The temperature at which individual granules becomerounded and take on a deeper color is taken as the softening point; thetemperature at which the material spreads on the glass or wets the glassis taken as the flowing point. j

I have found that I can prepare a compar-- ably hard product with thezinc chloride r alone. In this case the time of treatment is somewhatlonger. .Whether the catalytic effect shown in my experiments is due tothe acidic substances per se, or, to the addition products of theseacidic substances with the Parts by weight Smoked sheet 100 Zinc oxide 5Sulphur 5 Accelerator 1 cured at a temperature corresponding to 40 lbs.steam pressure gave the following results:

Time of Elongaggii Load at cure tron 610mg. break I have found that theproduct prepared as above not only'is a good accelerator of thevulcanization of rubber but it also im- Nor do I wish ber prepared withthe zinc chloride-hydroa chloric acid catalyzed productare shown by thefollowing tests made on a rubber prepared as noted above. This rubberwas first artifically aged by placing in a chamber heated to 70 C. andpassing warm fresh air over the rubber. A sample was tested at the endof each day.

Days Load at aged break Liza/in.

pressure. The results were as follows:

Hours Load at in the bomb break Lbs/in. 0 3325 48 3125 72 2625 celerator-antioxidant in the formula:

Parts by weight Smoked sheet- 100 Zinc oxide 5 Sulphur 5 .i-Lcceleratorantioxidant 3 Cured at temperature of steam at lbs/in for 30 minutes.Specimens of thls rubber O were then aged 1n a bomb at C. in anatmosphere or oxygen at 300 lbs/1n pressure and the following resultsobtained:

Hours in the ggfi bomb Lbs/in. 0 3100 48 3100 72 3150 What I claim is:

1. The process of making a combined rubber vulcanization accelerator andantioxidant which comprises condensing, under essentiall anhydrousconditions, acetaldehyde with aniline in the presence of an acid zincsalt as a catalyst.

2. The process of making a combined rubber vulcanization accelerator andantioxidant which comprises condensing, under es sentially anhydrousconditions, two moles of acetaldehyde with one mole of aniline in thepresence of an acid zinc salt asa catalyst;

3. The process of making a combined rubbervulcanization accelerator andantioxidant which comprises condensing, under essentiala ly anhydrousconditions, .acetaldehyde with aniline in the presence of zinc chlorideas a catalyst. I

. 4, The process of making a combined rubber vulcanization acceleratorand antioxi dant which comprises condensing, under essentially anhydrousconditions, acetaldehyde with aniline in the presence of zinc chlorideand hydrochloric acid as a catalyst.

5. The process of making a combined rub ber vulcanization acceleratorand antioxidant which comprises condensing, under essentially anhydrousconditions, two molesofacetaldehyde. with one mole of aniline in the,presonce of zinc chloride and hydrochloric acid as a catalyst. I

6. The process of makinga combined rub ber vulcanization accelerator andantioxidant which comprises partially condensing acetaldehyde andaniline in the presence of an 'acid zinc salt'and then adding a mineralacid thereto and completing said aldehyde-amine condensation whilemaintaining substantially anhydrous conditions throughout the process. 7i e I 7. The process of making a combined rubber vulcanizationaccelerator and antioxidant which comprises partially condensing twomoles of acetaldehydeand one mole of anilinein the presence of zincchloride and then-adding hydrochloric acid thereto and completing saidaldehyde-amine condensation while maintaining substantially anhydrousconditions throughout the process;

8. The process of making a combined. rubber vulcanization acceleratorand antioxidant which comprises partially condensing, under essentiallyanhydrous conditions, acetaldehyde and aniline in the presence of anacid zinc salt and then adding a mineral acid thereto and completingsaid aldehydeamine condensation said condensation reaction being carriedout in the absence of substantial amounts of water beyond that formed inthe reaction.

9. The process of making acombined rubber vulcanization, accelerator andantioxidant which comprises reacting, under essentially anhydrousconditions, a small amount of a zinc chloride-aniline compound, anilineand acetaldehyde.

10. The process of maldng a combined rubber vulcanization acceleratorand antioxidant which comprises reacting, under essentially anhydrousconditions, a small amount of a zinc chloride-aniline compound, one moleof aniline and two moles of acetaldehyde.

11. The process of making a combined rubber vulcanization acceleratorand antioxidant which comprises reacting a small amount of a zincchloride-aniline compound, one mole of aniline and two moles ofacetaldehyde, and then adding a small amount of hydrochloric acid tocomplete the reaction while maintaining substantially anhydrousconditions throughout the process.

12. The process of making a combined rubber vulcanization acceleratorand antioxidant comprising reacting aniline and acetaldehyde in thepresence of up to 5% of a zinc chloride- 7 aniline compound of theformula ZnClg. (G H NH while maintaining substantial- 1y anhydrousconditions.

13. The process of making a combined rub-- ber vulcanization acceleratorand antioxidant comprising condensing two moles ofacetaldehyde with onemole of aniline in the presence of upto 5% of an acid zinc salt andwhile maintaining substantially anhydrous conditions.

14. The process of makmg a combined rubber vulcanlzation accelerator andantioxidant comprising reacting aniline and acetaldehyde' in thepresence of up to 5% of a zinc chloride-- aniline compound, and adding asmall amount of hydrochloric acid to complete the reaction whilemaintaining substantially anhydrous conditions throughout the process.

15. The product prepared by condensing under substantially anhydrousconditions .acetaldehyde with aniline in the presence of an acid zincsalt, said product retaining said salt.

16. The product prepared by condensing I under substantially anhydrousconditions two moles of acetaldehyde with one mole of aniline in thepresence of an acid zinc salt, said product retaining said salt.

17. A product prepared by condensing un dersubstantially anhydrousconditions two moles of acetaldehyde with one mole of aniline in thepresence of less than 5% by weight 'of an acid zinc salt, said productretaming said salt. 7

18. A product prepared by condensing under substantially anhydrousconditions acetaldehyde with aniline in the presence of zinc chloride,said product retaining the zinc chloride. 1

19. A product prepared by condensing under substantially anhydrousconditions two moles of acetaldehyde with one mole of aniline in thepresence of zinc chloride, said product retaining said zinc chloride.

Signed, at Montreal, Quebec, Canada, this 12th day of March A. D. 1928.

'ADRIEN CAMERON.

